JP2021023842A - Composite semipermeable membrane - Google Patents

Abstract

To provide a composite semipermeable membrane that has practicable permeability and removability, and retains high salt removability after repeated contact with acid and alkali.SOLUTION: A composite semipermeable membrane has a microporous support layer, and a separation functional layer provided on the microporous support layer. The separation functional layer contains a crosslinked aromatic polyamide and the polyamide has a specific moiety.SELECTED DRAWING: None

Description

The present invention relates to a semipermeable membrane useful for selective separation of a liquid mixture, and particularly to a composite semipermeable membrane having practical permeability and selective separation and high durability.

Membranes used for membrane separation of liquid mixtures include microfiltration membranes, ultrafiltration membranes, nanofiltration membranes, reverse osmosis membranes, etc., and these membranes are beverages from, for example, salt and water containing harmful substances. It is used to obtain water, to produce industrial ultrapure water, to treat wastewater, and to recover valuable resources.

Most of the reverse osmosis membranes and nanofiltration membranes currently on the market are composite semipermeable membranes, and among them, a separation function composed of a crosslinked aromatic polyamide obtained by a polycondensation reaction between a polyfunctional amine and a polyfunctional acid halide. A composite semipermeable membrane (Patent Document 1-2) obtained by coating a layer on a microporous support membrane is widely used as a separation membrane having high permeability and selective separation.

However, if the composite semipermeable membrane is continuously used, dirt adheres to the membrane surface with the elapsed time of use, and the membrane permeation flux of the membrane decreases. Therefore, it is necessary to wash the chemical solution with an acid, an alkali, or the like after a certain period of operation, which causes a problem that the separation performance of the membrane is deteriorated.

Therefore, in order to maintain stable operation for a long period of time, it is desired to develop a composite semipermeable membrane having little change in membrane performance before and after washing with a chemical solution such as acid or alkali, that is, having high acid resistance and alkali resistance.

In order to improve the alkali resistance of the composite semipermeable membrane, a method of contacting the composite semipermeable membrane with a hydrogen ion concentration aqueous solution having a pH of 9 to 13 (Patent Document 3) is disclosed. Further, in order to improve the acid resistance of the composite semipermeable membrane, a method of bringing a cyclic sulfate ester into contact with the composite semipermeable membrane (Patent Document 4) is disclosed.

JP-A-63-137704 WO2010 / 096563 Japanese Unexamined Patent Publication No. 2006-102624 JP-A-2010-234284

In the various proposals described above, some membranes have excellent durability against acid and alkali chemical solutions, but a membrane having durability even when acid and alkali are repeatedly negotiated is desired. An object of the present invention is to provide a composite semipermeable membrane having water permeability and salt removing property that can withstand practical use, and further having high salt removing property even after repeated contact with an acid and an alkali.

A composite semipermeable membrane having a microporous support layer and a separation functional layer provided on the microporous support layer, the separation functional layer containing a crosslinked aromatic polyamide, and the polyamide (1). A composite semipermeable membrane characterized by having a partial structure represented by).

(Ar1 to 3 are aromatic rings having 5 to 14 carbon atoms which may have a substituent, R1 to R3 are hydrogen atoms or aliphatic chains of carbon atoms 1 to 10, and X is at least one. It is an atomic group having a positively charged group and at least one loaded electric group, and the number of carbon atoms contained in X is 20 or less.)

According to the present invention, a composite semipermeable membrane having practical water permeability and salt removability and further exhibiting high salt removability even after repeated acid-alkali tests can be obtained.

[1. Composite semipermeable membrane]
The composite semipermeable membrane according to the present invention includes a support membrane and a separation functional layer formed on the support membrane. The composite semipermeable membrane has separation performance as a reverse osmosis membrane or a nanofiltration membrane. The separation function layer has substantially separation performance, and although the support membrane allows water to pass through, it does not substantially have separation performance of ions and the like, and can give strength to the separation function layer.

(1) Support film In the present embodiment, the support film includes a base material and a microporous support layer. However, the present invention is not limited to this configuration. For example, the support film may not have a base material and may be composed only of a microporous support layer.

(1-1) Base material Examples of the base material include polyester-based polymers, polyamide-based polymers, polyolefin-based polymers, and mixtures or copolymers thereof. Of these, polyester-based polymer fabrics with high mechanical and thermal stability are particularly preferable. As the form of the cloth, a long fiber non-woven fabric, a short fiber non-woven fabric, and a woven or knitted fabric can be preferably used.

(1-2) Microporous Support Layer In the present invention, the microporous support layer is intended to give strength to a separation functional layer that does not substantially have separation performance such as ions and has substantially separation performance. Is. The size and distribution of the pores in the microporous support layer are not particularly limited. For example, it has uniform and fine pores or gradually larger fine pores from the surface on the side where the separation function layer is formed to the other surface, and the size of the fine pores on the surface on the side where the separation function layer is formed. A microporous support layer having a size of 0.1 nm or more and 100 nm or less is preferable. The material used for the support layer and its shape are not particularly limited.

The material of the microporous support layer includes, for example, homopolymers or copolymers such as polysulfone, polyether sulfone, polyamide, polyester, cellulose-based polymer, vinyl polymer, polyphenylene sulfide, polyphenylene sulfide sulfone, polyphenylene sulfone, and polyphenylene oxide. It can be used alone or in combination. Here, as the cellulosic polymer, cellulose acetate, cellulose nitrate and the like can be used, and as the vinyl polymer, polyethylene, polypropylene, polyvinyl chloride, polyacrylonitrile and the like can be used.

Of these, homopolymers or copolymers such as polysulfone, polyamide, polyester, cellulose acetate, cellulose nitrate, polyvinyl chloride, polyacrylonitrile, polyphenylene sulfide, and polyphenylene sulfide sulfone are preferable. More preferably, cellulose acetate, polysulfone, polyphenylene sulfide sulfone, or polyphenylene sulfone can be mentioned. Further, among these materials, polysulfone can be generally used because of its high chemical, mechanical and thermal stability and easy molding.

The mass average molecular weight (Mw) of polysulfone when measured by gel permeation chromatography (GPC) using N-methylpyrrolidone as a solvent and polystyrene as a standard substance is preferably 10,000 or more and 200,000 or less, more preferably. It is 15,000 or more and 100,000 or less.

When the Mw of polysulfone is 10,000 or more, preferable mechanical strength and heat resistance can be obtained as a microporous support layer. Further, when Mw is 200,000 or less, the viscosity of the solution is in an appropriate range, and good moldability can be realized.

For example, a solution of polysulfone in N, N-dimethylformamide (hereinafter referred to as DMF) is cast on a densely woven polyester cloth or non-woven fabric to a certain thickness and wet-coagulated in water. A microporous support layer can be obtained in which most of the surface has fine pores having a diameter of several tens of nm or less.

The thickness of the base material and the microporous support layer affects the strength of the composite semipermeable membrane and the packing density when it is used as an element. In order to obtain sufficient mechanical strength and packing density, the total thickness of the base material and the microporous support layer is preferably 30 μm or more and 300 μm or less, and more preferably 100 μm or more and 220 μm or less. The thickness of the microporous support layer is preferably 20 μm or more and 100 μm or less. In this document, unless otherwise specified, the thickness means an average value. Here, the average value represents an arithmetic mean value. That is, the thickness of the base material and the microporous support layer can be obtained by calculating the average value of the thicknesses of 20 points measured at intervals of 20 μm in the direction orthogonal to the thickness direction (plane direction of the film) in the cross-sectional observation. ..

(2) Separation Function Layer (2-1) Chemical Structure of Separation Function Layer The separation function layer contains a crosslinked aromatic polyamide. In particular, the separation functional layer preferably contains a crosslinked aromatic polyamide as a main component. The principal component refers to a component that accounts for 50% by weight or more of the components of the separation functional layer. The separation functional layer can exhibit high removal performance by containing 50% by weight or more of the crosslinked aromatic polyamide.

The aromatic polyamide in the present invention has a partial structure represented by (1) by an amide bond via its terminal carboxy group.

(Ar1 to 3 are aromatic rings having 5 to 14 carbon atoms which may have a substituent, R1 to R3 are hydrogen atoms or aliphatic chains of carbon atoms 1 to 10, and X is at least one. It is an atomic group having a positively charged group and at least one loaded electric group, and the number of carbon atoms contained in X is 20 or less.)
The repeating unit (structure in parentheses) in the formula (1) is preferably a polymer of a polyfunctional aromatic amine and a polyfunctional aromatic acid chloride.

The terminal X in the formula (1) has at least one positively charged group and at least one loaded electric group. Since the substituent of X is pH-independent, the structure does not change even when it comes into contact with an acid or an alkali, and swelling due to charge repulsion does not occur, so that acid resistance and alkali resistance are improved.
Further, having a positively charged group at the same time as the load electric group has an advantage that the charge on the film surface is neutralized and the adhesion of heavy metals and the like to the film surface is suppressed. Furthermore, having a charged group improves hydrophilicity, and good water permeability can be obtained during use.

The number of carbon atoms of X in the partial structure (1) is preferably 20 or less, more preferably 15 or less, still more preferably 10 or less. When the number of carbon atoms is 20 or less, the ratio of the hydrophobic site to the hydrophilic group becomes small, so that the water permeability of the membrane becomes large.

The number of carbon atoms existing between the positively charged group and the loaded electric group of X can be appropriately selected, but is preferably 1 to 4 from the viewpoint of removability. By immobilizing the cationic group in the vicinity of the anionic group, aggregation with the multivalent ion is suppressed and the removability is improved.

Examples of the positively charged group possessed by X include ammonium cation, phosphonium cation, imidazolium cation, pyridinium cation, and pyrrolidinium cation. From the viewpoint of viscosity at the time of dissolution and expansion of the molecular chain, imidazolium cation and pyridinium cation are more preferable. X may contain two or more positively charged groups, but preferably contains one or two positively charged groups.

X preferably has at least one functional group selected from a carbanion, a sulfo anion, and a phospho anion as a load electric group. An example of the structure of the load electric group is shown in the following formula. X may contain two or more load electric groups, but it is preferable that X contains one or two load electric groups.

Further, when the molar ratio of the semi-aliphatic amido groups and carboxyl group in the separation functional layer (semi-aliphatic amido group / carboxyl group) × 10 ² was x, when it is 2.5 ≦ x, high removability Found to have. Since the carboxy group tends to have electrostatic affinity with multivalent ions, the charge repulsion is attenuated and the salt removal rate is lowered depending on the quality of the treated water. When 2.5 ≦ x, the partial structure represented by (1) is sufficiently provided, so that removability is ensured.

The main chain portion of X may be a ring type or a chain type, and may be formed only by a saturated bond or may contain an unsaturated bond, and may be appropriately selected depending on the desired performance. it can.
The amount of functional groups in these polyamides can be determined, for example, by 13C solid-state NMR measurement. Specifically, the base material is peeled off from the composite semipermeable membrane to obtain a separation functional layer and a porous support layer, and then the porous support layer is dissolved and removed to obtain a separation functional layer. The obtained separation functional layer is subjected to DD / MAS-13C solid-state NMR measurement, and the integrated value of the peak of the carbon atom to which each functional group is bonded is calculated. The amount of each functional group can be identified from this integrated value. As the functional group measured by 13C solid-state NMR, specifically, a carboxy group, an amino group, an aromatic amide group, a semi-aliphatic amide group, and an aliphatic chain portion in X are assumed. The semi-aliphatic amide group means an amide group in which the atomic groups on both sides of the amide group are an aliphatic chain and an aromatic chain, respectively.

In the present invention, the difference between the zeta potential at pH 3 and the zeta potential at pH 10 is preferably 20 mV or less. It is more preferably 15 mV or less, still more preferably 10 mV or less. Zeta potential is a measure of the net fixed charge on the surface of the ultrathin film layer. The polyamide separation functional layer contains unreacted amino groups and carboxyl groups derived from polyfunctional amines and polyfunctional acid halides, and the zeta potential value changes depending on the degree of dissociation of these functional groups. At pH 3, the unreacted amino group is dissociated, and at pH 10, the unreacted carboxy group is dissociated. Further, it is considered that the positively charged group and the loaded electric group of X in the partial structure (1) dissociate at both pH 3 and pH 10. When the difference between the zeta potentials at pH 3 and pH 10 is 20 mV or less, the change in charge balance due to the pH change due to acid-alkali contact is small, so the hydrophilic change and electrostatic repulsion are small, and the performance even during repeated acid-alkali contact. Is hard to change.

The zeta potential can be measured by an electrophoretic light scattering photometer. For example, the separation functional layer surface of the composite semipermeable membrane is set in a flat sample cell so as to be in contact with the monitor particle solution for measurement. The monitor particles are polystyrene latex coated with hydroxypropyl cellulose and dispersed in a 10 mM- NaCl solution to prepare a monitor particle solution. By adjusting the pH of the monitor particle solution, the zeta potential at a predetermined pH can be measured. As the electrophoresis light scattering photometer, ELS-8000 manufactured by Otsuka Electronics Co., Ltd. or the like can be used.

2. 2. Method for producing composite semipermeable membrane (1) Method for forming separation functional layer The above separation functional layer is obtained by chemically reacting a polyfunctional aromatic amine, a polyfunctional aromatic acid chloride, and an aliphatic carboxylic acid derivative. The crosslinked aromatic polyamide, which is the main skeleton, is constructed by a polymerization reaction of a polyfunctional aromatic amine and a polyfunctional aromatic acid chloride.

The polyfunctional aromatic amine has two or more amino groups of at least one of a primary amino group and a secondary amino group in one molecule, and at least one of the amino groups is primary. It means an aromatic amine which is an amino group. Examples of the polyfunctional aromatic amine include o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, o-xylylene diamine, m-xylylene diamine, p-xylylene diamine, o-diaminopyridine, and m-. A polyfunctional aromatic amine in which two amino groups such as diaminopyridine and p-diaminopyridine are bonded to an aromatic ring at any of the ortho-position, meta-position, and para-position, 1,3,5-triaminobenzene. , 1,2,4-triaminobenzene, 3,5-diaminobenzoic acid, 3-aminobenzylamine, 4-aminobenzylamine and other polyfunctional aromatic amines. In particular, m-phenylenediamine, p-phenylenediamine, and 1,3,5-triaminobenzene are preferably used in consideration of selective separability, permeability, and heat resistance of the membrane. Above all, it is more preferable to use m-phenylenediamine from the viewpoint of easy availability and ease of handling. These polyfunctional aromatic amines may be used alone or in combination of two or more.

The polyfunctional aromatic acid chloride refers to an aromatic acid chloride having at least two chlorocarbonyl groups in one molecule. For example, the trifunctional acid chloride includes trimesic acid chloride and the like, and the bifunctional acid chloride includes biphenyldicarboxylic acid dichloride, azobenzenedicarboxylic acid dichloride, terephthalic acid chloride, isophthalic acid chloride, naphthalenedicarboxylic acid chloride and the like. Can be done. Considering the selective separability and heat resistance of the membrane, a polyfunctional aromatic acid chloride having 2 to 4 carbonyl chloride groups in one molecule is preferable. Trimesic acid chloride is more preferable in consideration of selective separability, permeability and heat resistance of the membrane. These polyfunctional aromatic acid chlorides may be used alone or in combination of two or more.

Here, it is preferable that at least one of the polyfunctional aromatic amine and the polyfunctional aromatic acid chloride contains a trifunctional or higher functional compound. As a result, a rigid molecular chain is obtained, and a good pore structure for removing fine solutes such as hydrated ions and boron is formed.

As a method of chemical reaction, the interfacial polymerization method is most preferable from the viewpoint of productivity and performance. Hereinafter, the step of interfacial polymerization will be described.

The steps of interfacial polymerization are (a) a step of contacting an aqueous solution containing a polyfunctional aromatic amine on the porous support layer and (b) a porous support layer in which an aqueous solution containing a polyfunctional aromatic amine is brought into contact. The step of contacting the polyfunctional aromatic acid chloride solution with the water, (c) the step of draining the organic solvent solution after the contact, and (d) washing the composite semipermeable membrane obtained by draining the organic solvent solution with hot water. Has a process.

In this column, an example is given when the support film includes a base material and a microporous support layer, but when the support film has a different configuration, the “microporous support layer” is referred to as a “support film”. It should be read as.

In the step (a), the concentration of the polyfunctional aromatic amine in the aqueous solution of the polyfunctional aromatic amine is preferably in the range of 0.1% by weight or more and 20% by weight or less, more preferably 0.5% by weight or more and 15% by weight. It is within the range of weight% or less. When the concentration of the polyfunctional aromatic amine is in this range, sufficient solute removal performance and water permeability can be obtained.

The contact of the polyfunctional aromatic amine aqueous solution is preferably performed uniformly and continuously on the microporous support layer. Specifically, for example, a method of coating the microporous support layer with a polyfunctional aromatic amine aqueous solution, a method of immersing the microporous support layer in the polyfunctional aromatic amine aqueous solution, and the like can be mentioned. The contact time between the microporous support layer and the aqueous solution of the polyfunctional aromatic amine is preferably 1 second or more and 10 minutes or less, and more preferably 10 seconds or more and 3 minutes or less.

After the polyfunctional aromatic amine aqueous solution is brought into contact with the microporous support layer, the liquid is sufficiently drained so that no droplets remain on the membrane. By draining the liquid sufficiently, it is possible to prevent the remaining portion of the droplet from becoming a film defect and deteriorating the removal performance after the formation of the microporous support layer. As a method of draining the liquid, for example, as described in JP-A-2-78428, a method of vertically grasping the support membrane after contact with the polyfunctional aromatic amine aqueous solution and allowing the excess aqueous solution to flow down naturally. Alternatively, a method of forcibly draining the liquid by blowing an air stream such as nitrogen from an air nozzle can be used. Further, after draining the liquid, the film surface can be dried to partially remove the water content of the aqueous solution.

In the step (b), the concentration of the polyfunctional aromatic acid chloride in the organic solvent solution is preferably in the range of 0.01% by weight or more and 10% by weight or less, and 0.02% by weight or more and 2.0% by weight or less. It is more preferably within the following range. This is because a sufficient reaction rate can be obtained when the content is 0.01% by weight or more, and the occurrence of side reactions can be suppressed when the content is 10% by weight or less.

The organic solvent is preferably immiscible with water, dissolves the polyfunctional aromatic acid chloride, and does not destroy the support film, and is inactive to the polyfunctional aromatic amine and the polyfunctional aromatic acid chloride. Anything is fine. Preferred examples include hydrocarbon compounds such as n-nonane, n-decane, n-undecane, n-dodecane, isooctane, isodecan, isododecane and mixed solvents.

The method of contacting the microporous support layer in which the organic solvent solution of the polyfunctional aromatic acid chloride is brought into contact with the polyfunctional aromatic amine aqueous solution is the method of coating the microporous support layer of the polyfunctional aromatic amine aqueous solution. You can do the same.

In step (c), the organic solvent is removed by the step of draining the organic solvent solution after the reaction. To remove the organic solvent, for example, a method of grasping the membrane in the vertical direction and naturally flowing down the excess organic solvent to remove the organic solvent, a method of drying and removing the organic solvent by blowing wind with a blower, a mixed fluid of water and air. A method of removing excess organic solvent can be used.

In step (d), the composite semipermeable membrane from which the organic solvent has been removed is washed with hot water. The temperature of hot water is 40 ° C. or higher and 100 ° C. or lower, preferably 60 ° C. or higher and 100 ° C. or lower.

In this way, a layer containing a crosslinked aromatic polyamide having a terminal carboxy group (formula (2) below) is formed.

(Ar1 to 3 are aromatic rings having 5 to 14 carbon atoms which may have a substituent, and R2 to 3 are aliphatic chains having 1 to 10 hydrogen atoms or carbon atoms.)
Next, the partial structure represented by (1) above is imparted to the crosslinked aromatic polyamide.

The partial structure is imparted by reacting a compound having at least one positively charged group and at least one loaded electric group and having a carboxy group reactive functional group with the terminal carboxy group of the crosslinked aromatic polyamide. .. Specifically, the amino group of the compound which has been N-alkylated with imidazole, histidine, and histamine as a starting material and then subjected to loading electricity is reacted with the carboxy group of the separation functional layer. Examples of the compounds to be reacted are shown below.

For a highly efficient and short-time reaction, it is preferable to use various reaction aids (condensation accelerators) as needed. As a condensation accelerator, sulfate, 4- (4,6-dimethoxy-1,3,5-triazine-2-yl) -4-methylmorpholinium chloride (hereinafter referred to as DMT-MM), 1- (3- (3-) Didimethylaminopropyl) -3-ethylcarbodiimide hydrochloride, N, N'-dicyclohexylcarbodiimide, N, N'-diisopropylcarbodiimide, N, N'-carbonyldiimidazole, 1,1'-carbonyldi (1,2,4) -Triazole), 1H-benzotriazole-1-yloxytris (dimethylamino) phosphonium hexafluorophosphate, 1H-benzotriazole-1-yloxytris (dimethylamino) phosphonium hexafluorophosphate, (7-aza Benzotriazole-1-yloxy) tripyrrolidinophosphonium hexafluorophosphate, chlorotripyrrolidinophosphonium hexafluorophosphate, bromotris (dimethylamino) phosphonium hexafluorophosphate, 3- (diethoxyphosphoryloxy) -1,2,3-benzotriazine-4 (3H) -one, O- (benzotriazole-1-yl) -N, N, N', N'-tetramethyluronium hexafluorophosphate, O- (7-azabenzotriazole-1-yl) -N, N, N', N'-tetramethyluronium hexafluorophosphate, O- (N-succinimidyl)-N, N, N', N'- Tetramethyluronium tetrafluoroborate, O- (N-succinimidyl) -N, N, N', N'-tetramethyluronium hexafluorophosphate, O- (3,4-dihydro-4-oxo-) 1,2,3-benzotriazine-3-yl) -N, N, N', N'-tetramethyluronium tetrafluoroborate, trifluoromethanesulfonic acid (4,6-dimethoxy-1,3,5- Triazine-2-yl)-(2-octoxy-2-oxoethyl) dimethylammonium, S- (1-oxide-2-pyridyl) -N, N, N', N'-tetramethylthiuronium tetrafluoroborate , O- [2-oxo-1 (2H) -pyridyl] -N, N, N', N'-tetramethyluronium tetrafluoroborate, {{[(1-cyano-2-ethoxy-2-oxo) Ethiliden) Amino] Oxy} -4-morpholinomethylene} Dimethylammonium hexafluorophosphate, 2-chloro-1,3-dimethylimidazolinium hexafluoro Phosphate, 1- (chloro-1-pyrrolidinyl methylene) pyrrolidinium hexafluorophosphate, 2-fluoro-1,3-dimethylimidazolinium hexafluorophosphate, fluoro-N, N, N Examples include', N'-tetramethylform amidineium hexafluorophosphate.

As a method of bringing the compound into contact, the reaction may be carried out by coating on the separation functional layer of the composite semipermeable membrane, or the membrane containing the separation functional layer is immersed in the compound or a solution containing the compound to react. You may let me. Alternatively, a composite semipermeable membrane element, which will be described later, may be prepared and then a solution containing the compound may be passed through and reacted.

The reaction time and temperature when the compound is applied as a solution or as it is to the composite semipermeable membrane can be appropriately adjusted depending on the type of the compound and the application method. When the compound is applied as a solution, the concentration of the solution is preferably 10 mmol / L or more. When it is 10 mmol / L or more, the carboxy group at the polyamide terminal of the functional layer reacts sufficiently with the compound, and the acid resistance and alkali resistance improving effect of the separation functional layer can be obtained.

Further, by converting the amino group existing in the crosslinked polyamide by a modification treatment by an appropriately selected chemical reaction, a new functional group can be introduced and the performance of the composite semipermeable membrane can be improved. Examples of the new functional group include an alkyl group, an alkenyl group, an alkynyl group, a halogeno group, a hydroxyl group, an ether group, a thioether group, an ester group, an aldehyde group, a nitro group, a nitroso group, a nitrile group, an azo group and the like. Be done. Among them, it is more preferable to introduce a nitro group or an alkyl group, which are neutral functional groups that do not dissociate when they come into contact with an acid or an alkali, because the performance does not change even if they come into contact with an acid or an alkali repeatedly.

(2) Method for Forming Support Film The microporous support layer used in the present invention is such as "Millipore Filter VSWP" (trade name) manufactured by Millipore Co., Ltd. or "Ultra Filter UK10" (trade name) manufactured by Toyo Filter Paper Co., Ltd. You can choose from a variety of commercially available materials, but the "Office of Saline Water Research and Development Progress Report" No. It can be produced according to the method described in 359 (1968).

Specifically, the method for forming the microporous support layer includes the following steps.
-A solution is obtained by dissolving the resin forming the microporous support layer in a solvent.
-Apply the obtained solution to the substrate.
-Immerse in a coagulating solution containing the non-solvent of the above resin.

3. 3. Utilization of composite semipermeable membrane The composite semipermeable membrane is provided with a large number of holes together with a supply water flow path material such as a plastic net, a permeation water flow path material such as a tricot, and a film for increasing pressure resistance as needed. It is wound around a cylindrical water collecting pipe, and is suitably used as a spiral type composite semipermeable membrane element. Further, the elements can be connected in series or in parallel to form a composite semipermeable membrane module housed in a pressure vessel.

Further, the above-mentioned composite semipermeable membrane, its elements, and modules can be combined with a pump for supplying supply water to them, a device for pretreating the supplied water, and the like to form a fluid separation device. By using this separation device, the supplied water can be separated into permeated water such as drinking water and concentrated water that has not permeated the membrane, and water suitable for the purpose can be obtained.

As the supply water treated by the composite semipermeable membrane according to the present invention, a liquid mixture containing 500 mg / L or more and 100 g / L or less of TDS (Total Dissolved Solids) such as seawater, brackish water, and wastewater is used. Can be mentioned. Generally, TDS refers to the total amount of dissolved solids and is expressed as "mass ÷ volume" or "weight ratio". According to the definition, a solution filtered through a 0.45 micron filter is evaporated at a temperature of 39.5 ° C. or higher and 40.5 ° C. or lower and can be calculated from the weight of the residue, but more simply, the practical salt content (S). Convert from.

The higher the operating pressure of the fluid separator, the better the solute removal rate, but the energy required for operation also increases, and considering the durability of the composite semipermeable membrane, water to be treated is applied to the composite semipermeable membrane. The operating pressure for permeation is preferably 0.5 MPa or more and 10 MPa or less. As the supply water temperature increases, the solute removal rate decreases, but as the temperature decreases, the membrane permeation flux also decreases, so that the temperature is preferably 5 ° C. or higher and 45 ° C. or lower. In addition, when the pH of the supplied water becomes high, scales such as magnesium may be generated in the case of supplied water having a high solute concentration such as seawater, and there is a concern that the membrane may deteriorate due to high pH operation. It is preferable to operate in.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the present invention is not limited thereto.

(Identification of functional group of X)
The base material was physically peeled off from the composite semipermeable membrane 5 m2, and the porous support layer and the separating functional layer were recovered. After drying by allowing to stand at 25 ° C. for 24 hours, it was added little by little to a beaker containing dichloromethane and stirred to dissolve the polymer constituting the porous support layer. The insoluble matter in the beaker was collected with filter paper. This insoluble matter was placed in a beaker containing dichloromethane and stirred to recover the insoluble matter in the beaker. This operation was repeated until the elution of the polymer forming the porous support layer in the dichloromethane solution could not be detected. The recovered separation functional layer was dried in a vacuum dryer to remove residual dichloromethane. The obtained separation functional layer was made into a powdery sample by freeze-grinding, sealed in a sample tube used for solid-state NMR measurement, and 13C solid-state NMR measurement was performed by CP / MAS method and DD / MAS method. For 13C solid-state NMR measurement, for example, CMX-300 manufactured by Chemagnetics can be used. An example of measurement conditions is shown below.
Reference substance: Polydimethylsiloxane (internal standard: 1.56 ppm)
Sample rotation speed: 10.5 kHz
Pulse repetition time: 100s
From the obtained spectrum, peak division was performed for each peak derived from the carbon atom to which each functional group was bonded, and the functional group amount ratio was quantified from the area of the divided peak.

(Zeta potential measurement)
The composite semipermeable membrane is washed with ultrapure water, and the separation functional layer surface of the composite semipermeable membrane is set in contact with the monitor particle solution in the plate sample cell. Electrophoretic light scattering photometer (ELS) manufactured by Otsuka Electronics Co., Ltd. -8000). As the monitor particle solution, a measuring solution in which the polystyrene latex monitor particles were dispersed in a 10 mM-NaCl aqueous solution adjusted to pH 3 and pH 10 was used.

Various characteristics of the composite semipermeable membrane are such that seawater adjusted to pH 7.0 (TDS concentration 3.5%, boron concentration about 5 ppm) is supplied to the composite semipermeable membrane at an operating pressure of 5.5 MPa to perform membrane filtration treatment. It was determined by measuring the quality of permeated water and supply water after that. What is TDS? Total Dissolved Solids
: Abbreviation for total dissolved solids.

(Membrane permeation flux)
The amount of membrane permeation of the supply water (seawater) was expressed as the membrane permeation flux (m3 / m2 / day) by the amount of permeation per day (cubic meter) per square meter of the membrane surface.

(Solute removal rate)
(Solute Removal Rate (TDS Removal Rate)) TDS Removal Rate (%) = 100 × {1- (TDS Concentration in Permeated Water / TDS Concentration in Supply Water)}
(Acid-alkali repeated contact test)
The composite semipermeable membrane was immersed in an aqueous sodium hydroxide solution adjusted to pH 13 under an atmosphere of 25 ° C. for 16 hours. Then, it was immersed in a sulfuric acid aqueous solution adjusted to pH 1 under an atmosphere of 25 ° C. for 16 hours. Subsequently, it was thoroughly washed with water. Durability was determined from the membrane permeation flux ratio and the TDSSP ratio before and after repeating this operation three times. In addition, SP is an abbreviation for Transparency Permeation: substance permeation.

Membrane permeation flux ratio = Membrane permeation flux after immersion / Membrane permeation flux before immersion TDSSP ratio = (100-TDS removal rate after immersion) / (TDS removal rate after 100-immersion)
(Preparation of membrane)
(Reference example 1)
A 16.0% by mass DMF solution of polysulfone (PSf) was cast on a polyester non-woven fabric (ventilation volume 2.0 cc / cm2 / sec) to a thickness of 200 μm under the condition of 25 ° C., and immediately immersed in pure water 5 A porous support membrane was prepared by leaving it for a minute.

(Comparative Example 1)
The porous support membrane obtained in Reference Example 1 is immersed in a 3% by mass aqueous solution of m-phenylenediamine (m-PDA) for 2 minutes, the support membrane is slowly pulled up in the vertical direction, and nitrogen is blown from an air nozzle. After removing excess aqueous solution from the surface of the support membrane, a decan solution at 40 ° C. containing 0.165% by mass of trimesic acid chloride (TMC) was applied so that the surface was completely wet in an environment controlled at room temperature of 40 ° C. After allowing to stand for 1 minute, the membrane was made vertical and the excess solution was drained and removed to obtain a composite semipermeable membrane having a crosslinked aromatic polyamide separation functional layer.

(Comparative Example 2)
(3-Vinyl imidazorio) Acetate 50 mM, N, N-dimethylacrylamide 50 mM, N-hydroxyethyl acrylamide 50 mM, photopolymerization initiator 2,2-dimethoxy-2-phenylacetophenone 10 mM mixed aqueous solution, 365 nm by UV irradiation device A polymer solution was obtained by irradiating with the ultraviolet rays of. The irradiation intensity of the UV irradiation device was set so that the value measured by the ultraviolet integrated light meter was 20 mW / cm2. A mixed aqueous solution prepared by adding divinyl sulfone to a 3% aqueous solution of the polymer solution so as to be 1% was applied to the composite semipermeable membrane obtained in Comparative Example 1, and then the excess solution was removed by spin coating. The mixture was kept in a hot air dryer at ° C. for 3 minutes to obtain a polymer-coated composite semipermeable membrane of Comparative Example 2.

(Comparative Example 3)
After mixing ((3-methacryloylamino) propyl) -dimethyl (3-sulfopropyl) -ammonium hydroxide, poly (ethylene glycol) methacrylate, and poly (ethylene glycol) dimethyl acrylate, 2,2'-azobis (2) After reacting with -methylpropionamidine) dihydrochloride at 60 ° C. for 1 hour by a radical polymerization method, glycidyl methacrylate was added and further reacted at 60 ° C. for 1 hour to obtain a polymer solution. An aqueous solution of 0.05% of the polymer was applied to the composite semipermeable membrane obtained in Comparative Example 1, the excess solution was removed by spin coating, and the mixture was held in a hot air dryer at 80 ° C. for 3 minutes for polymer coating. A composite semipermeable membrane of Comparative Example 3 was obtained.

(Example 1)
The composite semipermeable membrane obtained in Comparative Example 1 was mixed with 100 mmol / L 4- (4,6-dimethoxy-1,3,5-triazine-2-yl) -4-methylmorpholinium chloride and a carboxy group. As the reactive compound, a compound having a loading voltage Y, positive charge Z, n1 and n2 of the compound represented by Chemical Formula 4 as shown in Table 1 was brought into contact with an aqueous solution of pH 7 containing 100 mmol / L for 24 hours at 25 ° C. The composite semipermeable membrane of Example 1 was obtained.

(Example 2)
The composite semipermeable membrane obtained in Comparative Example 1 was mixed with 100 mmol / L 4- (4,6-dimethoxy-1,3,5-triazine-2-yl) -4-methylmorpholinium chloride and a carboxy group. As the reactive compound, the compound having the loading voltage Y, positive charge Z, n1 and n2 of the compound represented by Chemical Formula 4 as shown in Table 1 is brought into contact with an aqueous solution of pH 7 containing 100 mmol / L for 2 hours at 25 ° C., and acetic acid is further prepared. Was added to 100 mmol / L and then contacted for 20 hours to obtain a composite semipermeable membrane of Example 2.

(Example 3)
The composite semipermeable membrane obtained in Example 1 was further immersed in a 1 wt% potassium peroxymonosulfate aqueous solution for 30 minutes, immersed in a 0.1 wt% sodium hydrogen sulfite aqueous solution for 10 minutes, and then rinsed with water. A composite semipermeable membrane of Example 3 was obtained.
(Example 4)
A composite semipermeable membrane of Example 4 was obtained in the same manner as in Example 1 except that the carboxy group-reactive compound was set to 10 mmol / L.

(Examples 5 and 6)
As the carboxy group-reactive compound, the composite semipermeable membranes of Examples 5 and 6 were used in the same manner as in Example 1 except that the compounds shown in Chemical Formula 4 had positive charges and negative charges as shown in Table 1, respectively. A permeable membrane was obtained.

(Examples 7 to 9)
As the carboxy group-reactive compound, the composite semipermeable membranes of Examples 7 to 9 were used in the same manner as in Example 4 except that the compounds shown in Chemical Formula 4 had positive charges and negative charges as shown in Table 1, respectively. A permeable membrane was obtained.

Above comparative example, the molar ratio (semi-aliphatic amido group / carboxyl group) × 10 ² semi aliphatic amide group and a carboxyl group of the composite semipermeable membrane obtained in Example and the surface zeta potential in x, pH 3 Table 2 shows the difference in surface zeta potential at pH 10, the performance during production, and the performance after the acid-alkali repeated deterioration test. As shown in Examples, it can be seen that the composite semipermeable membrane of the present invention has high water permeability and removal performance, and also has high performance even after repeated contact with acid and alkali.

Claims (4)

A composite semipermeable membrane having a polyamide microporous support layer having an amphoteric charged group and having a terminal group converted, and a separation functional layer provided on the microporous support layer, and the separation functional layer is crosslinked. A composite semipermeable membrane containing an aromatic polyamide and having the partial structure represented by (1).

(Ar1 to 3 are aromatic rings having 5 to 14 carbon atoms which may have a substituent, R1 to R3 are hydrogen atoms or aliphatic chains of carbon atoms 1 to 10, and X is at least one. It is an atomic group having a positively charged group and at least one loaded electric group, and the number of carbon atoms contained in X is 20 or less.) The composite semipermeable membrane according to claim 1, wherein the difference between the surface zeta potential at pH 3 and the surface zeta potential at pH 10 of the separation functional layer is 20 mV or less. In the partial structure (1) of the separation functional layer, the positively charged group is an imidazolium group or a pyridinium group which may have a substituent, and the loaded electric group is a group selected from the following structural group. Item 2. The composite semipermeable membrane according to Item 1 or 2.

Wherein the molar ratio of the semi-aliphatic amido groups and carboxyl groups in the separating functional layer when the (semi aliphatic amido group / carboxyl group) × 10 ² was x, any one of claims 1 to 3 is 2.5 ≦ x The composite semipermeable membrane according to.
Semi-aliphatic amide group: An amide group in which the atomic groups on both sides of the amide group are an aliphatic chain and an aromatic chain, respectively.
x: Semi-aliphatic amide group / carboxy group